Time system



L. S. HARRISON TIME SYSTEM Filed April 19, 1935 2 Sheets-Sheet 1 INVENTOR.

7% ATTORNEY wdE Dec. 7, 1937.

| s. HARRISON TIME SYSTEM Filed April 19, 1935 2 Sheet-Sheet 2 IN VEN TOR.

g e ATTORNEY Patented I, 1937 UNITED STATES rATsu-T orrica signor to International Business Machines Corporation, New York, N. Y., a corporation of New. York Application April 19, 1935, Serial No. 17,245

6 Claims. ('01. 58-24) This invention relates to time systems in which the time indicating units are driven by synchronous or other constant speed motors running from the main lines used for distributing commercial alternating current supply. More particularly this invention relates to'the periodic synchronization of such motor driven clocks by a master clock.

An object of the invention is to provide periodic synchronization of a plurality of motor driven secondaries operating from commercial power supply lines. 1

Another object of the invention is to provide for synchronizing a plurality of time indicating units by superimposing a frequency different from that upon which the time indicating units normally operate over the lines on which said units operate.

Still another object is to provide a master clock for initiating the transmission of a superimposed frequency over lines from which time indicating units are operating on another frequency.

A still further-object is to provide for stepping time indicating units ahead faster than their normal rate by superimposing a frequency over the lines from which they operate higher than the frequency which normally operates them.

Another object is to provide for synchronizing a time indicating clock driven by a constant speed or synchronous motor .with a master clock by superimposing various frequencies at timed intervals over the lines on which the time.indieating clocks operate.

Various other objects and advantages of my invention will be obvious from the following particular description of one 'form of mechanism embodying the invention or from an inspection of the accompanying drawings, and the invention also constitutes certain new and novel features of the construction and combination of parts hereinafter set forth and claimed.

In the drawings:

Figs. 1 and 1a are a diagram of the wiring of a complete system showing diagrammatically pertinent parts of the secondary time indicating units.

The master clock in'it s general details may be of any desired form. For example, the master clock may be such as shown in the patents to J. W. Bryce, No. 1,390,018 and No. 1,687,491, dated September 6, 1921, and October 16, 1928, respectively. It is sufllcient here to state that the master clock carries on its minute hand staff three cams ll, H, and H which are fixed relatively to each other and make one revolution per hour. Such cams might correspond in their relationship to the master clock mechanism with cams l2, l3, and II in Patent No. 1,687,491, previously mentioned. In the applicant's embodiment the cams II, II, and I2 cooperate with contacts l3, I4, and I5, respectively. The cams make one revolution per hour which causes each of the contacts to open and close once during each cycle. In giving the timing of the various contacts the minutes and second of the hour will be designated. Which hour of the day it is,

is of no concern since the operations occur every power supply distribution system is shown with the neutral wire grounded. This is a system widely used in commercialpractice. It is further assumed that the three wire system is distributing cycle alternating current which is the general practice in most commercial fields in the United States. In the diagram the three wire system is represented as L1, L2 and N. N representing the grounded neutral. A switch S may represent the connection of the power supply from the outside to a three wire system within a given area such as a building, or a single department or floor in a building. Between the outside source of supply and the distributor system to which are connected the various time indicating units comprising the clock system to be synchronized is imposed a choke coil I6 located in the neutral wire. This coil is so designed to freely pass 60 cycle alternating current but to prevent the passage of 1200 cycle and 1800 cycle frequencies which are the frequencies to be used in connection with the applicant's preferred embodiment herein disclosed.

The time indicating units which will hereinafter be called secondary clocks to differentiate is a clutch element 28. This clutch element is engaged by a yoked arm 2| pivoted at 22 and biased in a clockwise direction by a spring 23 so that said clutch element normally engages and grips a gear 24 which is free to rotate about the shaft l8. The gear 24 meshes with a gear 25 which is fixed to the minute hand shaft 26 of the secondary clock to normally revolve the minute hand 26' once an hour. The usual reduction gear from the'minute hand to the hour hand as well as the hour hand has been omitted in the drawings as it is old and well known in every clock and has no part in the invention or the explanation of the operation of the system. Journaled on the shaft l8 and free to rotate thereabout is a gear 21 having fixed thereto a clutch element 28 adapted to be engaged by the clutch element 28. The gear 21 meshes with a reduction gear train 29 which in turn is meshed with a gear 38 fixed to the shaft 26. The gear ratios between the gear 38 and the gear 21 is such that the gear 21 will drive the gear 38 at a speed of 60 to 1. In the normal operation of the secondary clock, gear 24 is driving gear 25 and therefore gear 38 fixed to the same shaft will drive the gear 21 idly about the shaft IS. The secondary clock is further provided with a clutch magnet 3| which, when energized, attracts its armature which is fixed to the yoke arm 2| thus causing said arm to rotate counterclockwise about its pivot 22 to disengage the clutch element 28 from the gear 24 and engage it with the gear 21 which will then drive the shaft 26 at a speed 60 times greater, as previously explained.

The gear 24 at this time will be rotated idly about the shaft |8. Cooperating with arm 2| is a contact 33, normally open, which is adapted to be closed when the magnet 3| is energized. The secondary clock is further provided with two relays having relay coils 34 and 35. Relay coil 34 when energized causes relay contacts 36 to close. Relay coil 35 when energized causes relay contacts 31 and 38 to close. The relay which is actuated by coil 35 is also provided with an additional holding coil 39. The circuit of relay magnet 34 is provided with a blocking condenser 48 to permit said coil to be energized by an alternating current of 1200 cycle frequency only and the circuit of the relay coil 35 is provided with a blocking condenser 4| to permit said coil to be energized by an alternating current of 1800 cycle frequency only. Contacts 42, 43 and 44 are provided in each secondary and are operated by cam l8 fixed to the shaft 26 so that contact 42 opens and contacts 43 and 44 close at 60' 0" and contact 42 closes and contacts 43 and 44 open at 60' 30". This operation occurring once each hour. Each secondary is provided with two rectifier units 45 and 46 for the purpose of supplying holding coil 33 and clutch magnet 3| with unidirectional current.

Two motor generators 41 and 48 are provided with each system generator G41 is designed to generate current at a frequency of 1200 cycles and generator G48 is designed to generate current at a frequency of 1800 cycles. The circuits from generator G41'and G48 are provided with blocking condensers 49 and 58, respectively, to block off any back circuits of 60 cycle current from the power line.

Operation With the switch S closed so as to supply the distribution lines L1. N. and 1a with commercial 60 cycle current, the self-starting synchronous motor |1 operates on a circuit from L1 through wire 58, contact 42, wires 5| and 52, field coil 53 of the motor, wire 54 to line N. Assuming now that all secondary clocks are in synchronism with the master clock and each other. At the hour position of 59 10" as indicated by the master clock contact l3 closes and starts motors M41 and M48 of the motor-generator sets 41 and 48. The circuit is as follows: Line L1, wire 55,

' contact |3, motor M41 and M48 in parallel to line N. The generators G41 and G48 having now been started are ready to transmit 1200 cycles and 1800 cycles current, respectively, to the lines when the proper circuits are completed. At the master clocks indicated time of 59 20 contact I5 closes for two seconds establishing a circuit as follows: Generator G41, condenser 48, contact |5, wire 56, line N, wires 54, 51 and 58, relay magnet 34, condenser 48, ground connection 59, ground connection 58a to generator G41. As previously stated the choke coil IS in the neutral line does not permit anything other than 60 cycle frequency to pass so that the higher frequencies used in the operation are confined to the system. The relay coil 35 is provided with a blocking condenser 4| as previously stated which prevents it from. being effected by the 1200 cycle frequency which is now available. The relay coil 34 which is designed to operate on the 1200 cycle frequency is energized, however, closing relay contacts 36 which establishes the following circuit: Line L1, wire 58, contact 42, wires 5| and 68, rectifier 46, wires 6| and 62, contacts 36 (now closed), clutch magnet 3|, wires 63, 51, and 54, line N.

The rectified current energizes clutch magnet 3|, rocking arm 2| counterclockwise and causing contacts 33 to close, thus establishing a stick circuit through clutch magnet 3| as follows: Line L1, wire 58, contact 42, wires 5| and 68, rectifier 46, wires 6| and 64, contacts 33 (now closed) clutch magnet 3|, wires 63, 51 and 54, line N. Contact I5, and consequently contact 36 is closed for only two seconds so that the stick circuit through contact 33 holds the magnet 3| energized until the speed up operation is completed.

The result of energizing magnet 3| as previously explained, is to throw clutch element 28 into engagement with gear 21 and speed up the operation of the secondary clock. When the secondary clock reaches the hour position, cam l8 causes contact 42 to open and contacts 43 and 44 to close. The opening of contact 42 breaks the circuit to the motor |1, thus stopping the secondary clock. It also breaks the circuit through clutch magnet 3| deenergizing said magnet, thus openirm contact 33 and returning clutch element 28 to its normal position in engagement with gear 24. All secondary clocks have now been stepped up ahead of the master clock to thehour position, but this variation of a few seconds of time during this one period of the hour is not objectionable or noticeable in general practice.

When the master clock reaches the 60 0" position contacts |4 close for two seconds and establish the following circuit: Generator G48, condenser 58, contacts |4, wire 56, line N, wires 54, 51, 58 and 65, relay coil 35, condenser 4|, ground connections 58 and 59a, to generator G48. The 1800 cycle current now being transmitted energizes magnet 35, but not magnet 34 as previously explained, causing relay contacts 31 and 28 to close and establish the motor circuit again to aromas start the operation of the secondary clock at the even hour (60' 0" position) as follows:

Line L1, wires 88 and 66, contacts 38, (now closed), wire 51, contacts 43 (now closed), wires SI and 52, motor fleld coil 53. wire 51, line N. Since the contact H is only closed for two seconds, a holding coil is brought into circuit to hold contacts 31 and 38 closed. This circuit is as follows: Line Ll, wires 60' and 68, contacts 38, wire 61, contacts 43, wires H and 60, rectifier 46, contact 44 (now closed), wire 88, contact 31, holding coil 39, wires 65, 58, 6! and 54, line N. The correction operation is now completed and the clocks are in synchronous operation for the ensuing hourly period at the end of which the operation is repeated. Ten seconds after the hour (60' 10") contact i3 opens and breaks the circuit to the motors of the motor-generator sets I and 48. At thirty seconds after the hour (60' 30") contact 42 closes and contacts 43 and 44 open thus reestablishing their original and normal positions.

The operation above described takes place every hour and it is obvious that any secondary clocks that are behind the others will have an opportunity to speed up to the hour position during the forty seconds or any part thereof that they may hold their clutch magnet energized. Each secondary as it reaches its hour position independent of the others, cuts out its own motor circuit and releases its own clutch magnet In the case of fast clocks, as they arrive at their hour position ahead of time, they will open contacts 42 and break their own motor circuit, holding the clock stopped on the hour position until released by the master clock.

While all the fundamental novel features of the invention as applied to a single modification have been shown, described and pointed out in the accompanying specification, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated, and in its operation, may be made by those skilled in the art without departing from the spirit of the invention. I intend to be limited therefore only as indicated by the scope of the following claims.

What is claimed is as follows:

1. A clock system including a master clock and one or more synchronous motor driven secondary clocks connected to lines extending to the master clock, said lines normally carrying a low frequency current for normally advancing said secondary clocks at a time keeping rate, means for supplying high frequency currents having different frequency characteristics, to said lines, and means in said secondary clocks responsive to said high frequency currents for controlling the synchronization of said secondary clocks with respect to the master clock, said means including means responsive to a high frequency current of one frequency characteristic to periodically advance said secondary clocks which are slow with respect to the master clock at a rate of speed greater than said normal time keeping rate. means to interrupt clock advance upon a clock reachirm a determined time as determined by the chronological condition of each clock, and means controlled by a high frequency current of another frequency characteristic for restarting the clocks whereby they may resume normal advance under control of the low frequency current.

' 2. A clock system including a master clock and one or more synchronous motor driven secondary clocks connected to lines extending to said mas- BEST AVAILABLE COPY 3 ter clock, said lines normally carrying commercial circuit of a low frequency suitable for normally advancing said secondary clocks at a time keeping rate, means for supplying high frequency currents of different frequency characteristics to said lines, said means including master clock controlled means for controlling the supply of high frequency currents to the line wherein said high frequency currents are supplied to the lines for a determined time during a certain period and are cut on from the lines during the remaining time of said period, and means in said secondary clocks responsive to said high frequency currents for controlling the synchronization of said secondary clocks with respect to the master clock, said means including means responsive to a high frequency current of one frequency characteristic to periodically advance said secondary clocks which are slow with respect to the master clock at a rate of speed greater than said normal time keeping rate, means to interrupt clock advance upon a clock reaching a determined time as determined by the chronological condition of each clock, and means controlled by a high frequency current of another frequency characteristic for restarting the clocks whereby they may resume normal ad vance under control of the low frequency current.

3. A clock system including a master clock and one or more synchronous motor driven secondary clocks connected to lines extending to the master clock, said lines normally ca ying commercial current of a low frequency suitable for normally advancing said secondary clocks at a time keeping rate, means for supplying high frequency currents of different frequency characteristics to said lines to synchronize said clocks with respect to the master clock, and means in each secondary clock responsive to currents of different frequency characteristics for controlling the synchronization of said secondary clocks with respect to the master clock, said means including, means responsive to a high frequency current of one frequency characteristic to periodically advance the secondary clocks which are slow with respect to the master clock at a rate of speed more rapid than the normal time keeping rate, means controlled by the chronological position of each secondary clock for interrupting clock advance and simultaneously conditioning said clock for restarting and means responsive to a current of another frequency for causing said secondary clock to resume normal advance.

4. A synchronous motor driven clock normally operated from a power distributing system carrying a low frequency current for commercial power uses, means for supplying high frequency currents of different frequency characteristics to said power distribution system, synchronizing means in said clock including means controlled by a high frequency current of one frequency characteristic to accelerate the drive of the clock from the driving motor, means for stopping the synchronous motor drive of said clockwhen it reaches a certain chronological condition, and means controlled by a high frequency current of another frequency characteristic for resuming normal operation-of said clock by the low frequency power current.

5. An electric clock system including a master clock and one or more secondary clocks, a syn chronous motor in each secondary clock for driving the same, a power distribution system transmitting commercial current supply at a low fre- BEST AVAILABLE COPY quency extending to said master clock and to which each synchronous motor is connected to to the power distribution system simultaneously with the low frequency commercial current, and means in each secondary clock responsive to high frequency currents of diflerent frequency characteristics for synchronizing each secondary clock periodically with respect to the master clock, said means including means responsive to a high frequency current of one frequency characteristic for advancing said clocks which are slow with respect to the master clock at a rate faster than said time keeping rate until they reach a certain chronological position, means controlled by each secondary clock when said chronological position is reached for disconnecting the synchronous motorassociated therewith from the pswer distribution system to interrupt advance of said secondary clock and means controlled by a high frequency current of another frequency characteristic for reconnecting said synchronous motor to the power distribution system to resume advance of said secondary clock at a time keeping rate.

*- "6. Anelectric clock adapted to be controlled by currents of different frequencies including a synchronous motor operated by a current of one frequency, time indicating, means. a gear train connected to said time indicating means, a clutch element driven by said motor and normally en- 4 aging said gear train to drive the time indicating means at a time keeping rate of speed, a second gear train having a gear ratio different than the first named gear train and connected to said time indicating means, means responsive to a current of a second frequency for causing said clutch element to engage said second gear train and disengage said first gear train to drive said time indicating means at a rate of speed faster than said normal time keeping rate, means controlled by the chronological position of said time indicating means for arresting the operation of said motor to interrupt the advance of said time indicating means and for causing said clutch element to disengage said second gear train and to reengage said first gear train, and means responsive to a current of a third frequency for causing said motor to resume operation from the current of the first mentioned frequency to advance the time indicating means at a time keeping rate.

LAURENCE S. HARRISON. 

